title: Effect of probiotic bacteria on the intestinal microbiota in irritable bowel syndrome.
abstract: OBJECTIVE
  In irritable bowel syndrome (IBS), the gut microbiota may be altered. Probiotic bacteria appear to be therapeutically effective. We characterized the mucosa-associated microbiota, and determined the clinical and microbiological effects of orally administered probiotic bacteria, in patients with IBS.
  
  
  METHODS
  Mucosal microbiota from rectal biopsies of IBS patients and controls were assessed on the V1 and V2 variable regions of the 16S ribosomal RNA gene amplified using 454 pyrosequencing. Clinical symptoms and changes in mucosal microbiota were assessed in IBS patients before and after 4 weeks of treatment with probiotic mix VSL#3.
  
  
  RESULTS
  Ten IBS subjects (eight female; mean age 46 years) were included. At week 4 of probiotic therapy, six patients showed symptom improvement on global symptom assessment compared with baseline (P = 0.031). Before therapy, intestinal microbiota of IBS subjects differed significantly from that of healthy controls, with less diversity and evenness than controls (n = 9; P < 0.05), increased abundance of Bacteroidetes (P = 0.014) and Synegitestes (P = 0.017), and reduced abundance of Actinobacteria (P = 0.004). The classes Flavobacteria (P = 0.028) and Epsilonproteobacteria (P = 0.017) were less enriched in IBS. Abundance differences were largely consistent from the phylum to genus level. Probiotic treatment in IBS patients was associated with a significant reduction of the genus Bacteroides (all taxonomy levels; P < 0.05) to levels similar to that of controls.
  
  
  CONCLUSIONS
  In this pilot study, global and deep molecular analysis demonstrates an altered mucosal microbiota composition in IBS. Probiotic leads to detectable changes in the microbiota. These effects of probiotic bacteria may contribute to their therapeutic benefit.
authors.affiliation: Institute of Digestive Disease, Department of Medicine and Therapeutics, Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong.
authors.forename: Siew Chien
authors.initials: SC
authors.lastname: Ng
authors.forename: Emma F C
authors.initials: EF
authors.lastname: Lam
authors.forename: Tommy T Y
authors.initials: TT
authors.lastname: Lam
authors.forename: Yawen
authors.initials: Y
authors.lastname: Chan
authors.forename: Wendy
authors.initials: W
authors.lastname: Law
authors.forename: Pete C H
authors.initials: PC
authors.lastname: Tse
authors.forename: Michael A
authors.initials: MA
authors.lastname: Kamm
authors.forename: Joseph J Y
authors.initials: JJ
authors.lastname: Sung
authors.forename: Francis K L
authors.initials: FK
authors.lastname: Chan
authors.forename: Justin C Y
authors.initials: JC
authors.lastname: Wu
mesh_terms: D000284:Administration, Oral; D000328:Adult; D001419:Bacteria / Q000235:genetics / Q000302:isolation & purification*; D005260:Female; D005798:Genes, Bacterial / Q000235:genetics; D006801:Humans; D007413:Intestinal Mucosa / Q000382:microbiology*; D043183:Irritable Bowel Syndrome / Q000382:microbiology* / Q000628:therapy; D008297:Male; D008875:Middle Aged; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D019936:Probiotics / Q000008:administration & dosage*; D012336:RNA, Ribosomal, 16S
chemical_list: D012336:RNA, Ribosomal, 16S
keywords: IBS; intestinal microbiota; probiotics; pyrosequencing